Online C++ Compiler

To start your programming journey you first need to understand what compilers are. Compilers are the computer software that converts your high-level source code to executable machine-level instructions made up of 0s and 1s, that can be understood by the computer.

Compilers scan the high-level code line by line and show different kinds of errors present in the code in the command line.

Scaler Topics comes with a user-friendly IDE to compile, test, and run C++ programs online easily for free.

Working of the Online C++ Compiler (IDE)

Scaler Topics provides us with one of the best c++ compilers that is easily operated and that supports multiple programming languages.

Given below are some of the steps of our Compiler which users might find helpful:

The first step is your need to Sign-In to use the features of this compiler. It is possible to run your code without signing in but you will not have a track to your previous codes here, so it's advisable to sign in to enjoy its cool features. Click on the button present at the top right corner and a window will appear.

  • Code Editor: Write code in the code editor (which has syntax highlighting for more code readability). For users who are logged into the Scaler Topics Platform, the total number of characters in their code can go up to five thousand characters. For non Scaler Topics Users, their C++ code can have up to five hundred characters.
  • RUN: In order to run a C program, a user can write C++ code in the editor and then click on the ‘RUN’ button after selecting the appropriate compiler version.
  • SAVE: The C++ code written in the editor can be saved by clicking on the ‘SAVE’ button on the top right corner of the webpage. The saved codes can be accessed using the ‘MY SNIPPETS ’ button of the webpage.
  • STDIN & STDOUT: In order to feed input to the C++ Code, users can use the Standard Input (stdin) console of our compiler and the output of the code appears on the Standard Output (stdout) of the compiler.
  • SAVE: The programs saved can be made public - available for all - or private - accessible to only the code owner.
  • FORK: Public code snippets can also be forked or downloaded in the ‘NEW’ section using the ‘FORK’ button. After forking a code, one can reuse it as per requirement.
  • SHARE: Now that you have your code ready, you might need to share it with people. Our compiler also supports sharing of code in Read-Only Format. This can be done using the ‘SHARE’ button on the top right corner of the webpage.

Given below is a sample code snippet that adds two numbers in C++:

Learn C++ Programming

C++ is a programming language that allows programmers to write commands that can be understood by computers. It is a formal way of explaining the set of instructions to perform a particular task.

Why Learn C++?

C++ is one of the highly demanded programming languages by various tech giants. It has the following features:

  • C++ allows writing programs that can be run quickly and that's why it's commonly used for developing complex game applications and business applications. For example, Google Chrome, Microsoft Office.
  • It is easy to learn as it has simple code syntax that can be easily understood.
  • It is an Object-Oriented programming language, i.e. it can visualize problems in terms of objects rather than in the form of procedures for solving them.
  • It is a mid-level programming language.
  • It has a lot of built-in libraries that help programmers in making development fast and efficient which saves time.
  • C++ also supports dynamic memory allocation and memory management techniques.

C++ Syntax

C++ has various syntax rules that are scanned by IDEs. Following are some of the basic syntax that one should know to start their programming career in C++:

Loops (for loop, while loop, do-while loop)

Loops are used when there is the need to repeatedly execute a block of statements, for example printing the numbers from 1 to 5. Let’s execute this using all the three loops in our Scaler Topics IDE.

for loop




while loop




do while loop




Conditional Statements (if/else, switch case)

C++ supports various decision-making statements like if, if..else, nested if, switch case. We have discussed the basic one:





An array is a collection of data that are of similar data types. It stores data in a contiguous memory allocation. They can be one-dimensional or two-dimensional.





Functions are defined as a block of code that gets executed when it is code by some other function. It allows you to re-use the block of code whenever needed. There are the following parts in a function:

Function Declaration:

Function call:

Function Definition:


How to Write a C++ Program?

We have gone through various examples for C++ programs, but haven’t discussed what these lines of code meant. In this section, we will cover how, to begin with writing a C++ code. Below is the simple sample code which we will be understanding:

  • Line 1: It contains the header file that is useful for writing the code. Each header file has its own importance. The one mentioned here is responsible for performing standard input/output operations, for example, to print the “Hello World!!” message on the screen. The headers starting with # are the directives and these are interpreted by the preprocessor.

    There are various other headers like , , etc, that act as a helping hand for the programmers to code.

  • Line 2 and Line 5: It has a main() function with the return type int. This is the entry point for any program. A C++ program begins its execution form here and compiles each line of code till it reaches an end. Every time a function block starts and ends with the pair of { }.

  • Line 3: This C++ statement has three parts, the first one is cout which is an object of class ostream defined under header. It is used to print output on the console. The next part is the insertion operator << which specifies what follows should be inserted in the standard output stream and the last part is the string that needs to be printed on the screen. You can also use \n or endl to move the next output to the new line.

  • Line 4: This is the return statement for a function. It is used to return the value of the function. Here, since the main function is not returning any specific value so by default it returns 0. You can also use the void keyword before the function name if it is not returning anything.

Note: The statements in C++ end with a semicolon (;)

How to Compile and Run the C++ Programs Online?

Now, it's time to translate our source code from high-level languages to machine-level language i.e. binary instructions that can be understood by the processor. For this, we need to compile our code. If you are using an online compiler, simply click on the compile button (or Run button if there is no compile button present). If you want to compile your code from cmd or terminal, open it at the location where you have your program file. Assuming you have installed the gcc compiler, run this command.

The next step is to run the code (assuming that there are no errors). For online IDEs, click on the Run button, and for gcc compiler run the below command:

Additional Resources


  • Online IDE: IDE is an acronym for Integrated Development Environment. Online Integrated Development Environments help programmers code in various languages and run, compile and debug their codes online without having the need to download the respective programming compilers.
  • Compiler: In computing, a compiler is a computer program that is used to translate computer codes written in one programming language into another language.
  • Interpreter: Like Compilers, interpreters are also used to translate computer codes written in one programming language into another language. However, the difference between the two is that compilers compile the entire source code into machine code at once while interpreters convert the source code into machine code line by line.
  • Code Editor: A code editor is software used by programmers to code. Most code editors provide various features like syntax highlighting to make the code written on them more readable.
  • Coding Ground: Coding grounds are platforms that can be used to write and run codes written in various languages.